There are various types of reciprocating pumps used for pumping cementitious materials. A common form that these types of pumps take is that of a ball valve pump; that is, the flow of material through the pump is controlled by an inlet (suction) valve and a discharge valve, each of which consists of a ball and a seat. Thus, on the suction stroke the inlet ball unseats, allowing material to enter the pump housing, while the discharge valve is seated, preventing drawback of previously pumped material. On the discharge (extend) stroke, the discharge valve is forced open and the inlet (suction) valve is seated, thus preventing blowback into the hopper. This action is very simple, but very effective.
The intended purpose of these pumps is to transport and inject under pressure various cementitious materials ranging from fluid slurries to heavy sanded grouts, such as cement slurries, sanded cement mixes, bentonite mixes (with or without sand), repair mortars, high strength non-shrink grouts and self-leveling products. Common characteristics of these materials are that they are often fluid or semi-fluid, have a relatively high specific gravity and are often granular in composition. When the material is moving freely out of the pump and through hoses, the material generally maintains its integrity. However, under pressure, and particularly if the linear velocity is reduced, the materials tend to settle out of suspension and agglomerate within the hose and the discharge portion of the pump.
When this occurs, the pressure within the entire discharge system can increase to the maximum pump capacity. Due to the ball valve design, there is no internal means to relieve this pressure buildup. Therefore, the operator will customarily actuate a manually operated pressure dump valve to relieve system pressure so the hoses can safely be disconnected and cleaned. Unfortunately, due to the geometry of these types of valves, there is usually a considerable distance between the flow line and the actual valve mechanism, and often this conduit becomes plugged with material, rendering the valve useless and frequently necessitating its replacement.
Referring to FIGS. 1 and 2, there are show sectional views of a prior art pressure relief valve 120 in the closed and open positions, respectively. The pressure relief valve 120 is connected to a T-connector 122 by means of a fluid connector 126. Cementitious material is displaced in either direction along axis X-X′ under pressure within a conduit (not shown for simplicity) to which the T-connector 122 is coupled. Connector 126 may be of conventional design such as of the threaded, pinned or U-clip type. Pressure relief valve 120 includes a housing 128 having a cylindrical expanded portion through which extends a cylindrical slot, or opening, 128a. Disposed within the cylindrical slot 128a and free to rotate therein is a cylindrical insert 130. Cylindrical insert 130 includes an elongated, linear slot 130a extending along a portion of the length of the cylindrical insert. Attached to one end of the cylindrical insert 130 by conventional means such as a threaded member 134 in the form of a screw is a handle 132. Disposed on the distal end of the valve housing 128 is a discharge end 136 of the pressure relief valve 120. Rotation of the handle 132 in the direction of arrow 140 shown in FIG. 1 causes counterclockwise rotation of the valve's cylindrical insert 130. 90° degree rotation of handle 132 from its orientation shown in FIG. 1 results in a corresponding 90° rotation of the valve's cylindrical insert 130 so that its elongated, linear slot 130a is aligned with the lengthwise axis Y-Y′ of the pressure relief valve's housing 128 as shown in the sectional view of FIG. 2. In this position, the cementitious material flowing under pressure within T-connector 122 is discharged via the discharge end 136 of the pressure relief valve 120 so as to reduce the pressure within the conduit. As discussed above, one of the problems with this arrangement is the dead space 138 disposed between the conduit-connected portion of the T-connector 122 and the pressure relief valve 120. This dead space 138 disposed within the T-connector 122 and a portion of the pressure relief valve 120 is shown in FIG. 1 as having a length “Z”. It is within this dead space 138 that the cementitious material tends to collect and set, or harden, when the cementitious material is displaced through the conduit and T-connector 122 combination with the pressure relief valve 120 in the closed position as shown in FIG. 1. This situation makes cleaning of the grout pumping system after use very difficult and may even necessitate replacement of the T-connector 122 and pressure relief valve 120 combination.
The present invention avoids this problem encountered in the prior art by positioning the active part of the valve directly in the flow line to eliminate any buildup of the cementitious material between the flow line and the valve, thus providing a positively acting valve capable of relieving system pressure and preventing plugging of the flow line and valve combination by the pumped material.